Co–Mn spinel oxides trigger peracetic acid activation for ultrafast degradation of sulfonamide antibiotics: Unveiling critical role of Mn species in boosting Co activity

Activation of peracetic acid (PAA) to generate powerful oxidizing species has become a promising advanced oxidation processes (AOPs) in wastewater treatment, yet the development of low-cost and high-performance activators is still a primary challenge. Herein, a range of Co-Mn spinel oxides (Co3-xMnxO4) with varying levels of Co and Mn were successfully elaborated, in which Co1.1Mn1.9O4 exhibited remarkable performance in PAA activation, outperforming most reported heterogeneous catalysts. Extensive quenching experiments and electron spin resonance (ESR) analysis indicated that acetylperoxyl radical (CH3C(O)OO●) was the predominated oxidizing species responsible for sulfamethoxazole (SMX) degradation. Density functional theory (DFT) calculations revealed that doping with Mn not only promoted the electron transfer and accelerated reduction of Co(III) to Co(II), but also lowered the energy barrier for PAA activation. Moreover, the prominent chemisorption and activation of PAA with Co1.1Mn1.9O4 was also benefitted from the significant role of Mn in optimizing the distribution of bonding and antibonding states on Co 3d orbitals. Unexpectedly, high levels of Cl-greatly facilitated SMX degradation due to the mass production of HOCl from the chain reactions of various radicals with Cl-. This work provides new insights into bimetallic activation of PAA, and the knowledge obtained will further advance the application of PAA-based AOPs.